The present invention relates to a drilling method and the relevant drilling machine for stacked boards, particularly for printed circuits. As it is known these boards are formed with a glass resin covered with a layer of copper and are drilled before the photoetching of the circuit metal.
In the series production, the drilling machines are normally controlled by a numerical control apparatus, provided with a program unit recording the positions of the requested holes.
The known drilling machines of the said type normally drill each time a package of some boards, generally three boards, which is prepared with the addition of two auxiliary or dummy boards, one as bottom and one as top. The bottom board is provided to allow the full drilling of the lower board of the package and therefore will be partially drilled together with the package, while the top board must be drilled too to prevent the tool, by engaging the metallic layer not covered by another board, from splintering it.
The boards of the package are mutually connected with pins, the projection of which serves as reference for positioning the package on the drilling machine. The packaging operation is previously effected, whereas the packages of boards are manually loaded on the drilling machine and unloaded after the drilling. Therefore the known drilling machines, between one drilling cycle and the other, require some very long dead times, whereby in the production of the printed circuits this operation is prolonged. Furthermore, the two dummy boards of the drilled package form wastage, generally of the order of 40% of all loaded boards, whereby the manufacture of the printed circuits is generally very expensive.